Temperature-independent ceria- and Pt-doped nano-size TiO2 oxygen lambda sensor using Pt/SiO2 catalytic filter

We report for the first time the elimination of overlap of TiO2-based oxygen sensors responses in the rich and lean regions at various temperatures, by using a 1.0 wt% Pt/SiO2 catalytic filter located in front of the sensors. Nano-size TiO2 was prepared by a microemulsion method and then doped with 1.0 wt% Pt and 10.0 wt% CeO2 by an impregnation method. The sensor was exposed to synthetic exhaust gases with λ values in the range of 0.8–1.4. All of the sensors show low-high transitions at about λ = 1.0. However, without the use of the catalytic filter, the responses of the sensors in the rich and lean regions overlap at different temperatures. By using the catalytic filter only CO or O2 reaches the sensors. Thus, the low-high transition gap strongly enhances, and the overlap of the sensors responses between the rich and lean regions at various temperatures is eliminated. The transition gaps between λ = 0.9 and λ = 1.1 regions at 700 °C increase from 6.1, 17.5, and 14.5 times changes for TiO2, Pt/TiO2, and Ce/TiO2 without the filter to 431, 1881, and 16,149 times changes, respectively, when the catalytic filter is placed prior to the sensors.